Lore, I have industrial noise induced hearing loss as a result of a job I had in my youth. Annoyingly the damage mostly knocks out human voices.
I struggle to have conversations in the office with the back ground noise of regular PC/printer cooling fans blotting out speech but...
I had absolutely no problem with the sound quality of your videos.
I don't know who complained about your audio quality but I think the problem is with their equipment and not yours. Your voice sounded crystal clear with my midrange sound card and speakers even at low volume levels versus my gaming rigs fans.
Don't think you need the mic in shot.